2 Invoking groff

This section focuses on how to invoke the groff front end. This
front end takes care of the details of constructing the pipeline among
the preprocessors, gtroff and the postprocessor.

It has become a tradition that GNU programs get the prefix ‘g’ to
distinguish it from its original counterparts provided by the host (see
Environment, for more details). Thus, for example, geqn is
GNU eqn. On operating systems like GNU/Linux or the Hurd, which
don’t contain proprietary versions of troff, and on
MS-DOS/MS-Windows, where troff and associated programs are not
available at all, this prefix is omitted since GNU troff is the
only used incarnation of troff. Exception: ‘groff’ is never
replaced by ‘roff’.

In this document, we consequently say ‘gtroff’ when talking about
the GNU troff program. All other implementations of troff
are called AT&Ttroff, which is the common origin of all
troff derivates (with more or less compatible changes).
Similarly, we say ‘gpic’, ‘geqn’, etc.